Investigation of Partial Discharge Mechanism by Simultaneous Measurement of Current Waveform and Light Emission

Abstract

SUMMARYWe observed current pulse waveforms of partial discharge (PD) in SF 6 gas so as to investigate the PD mechanism. We also measured light intensity and light emission image of PD simultaneously under different conditions of applies voltage and SF 6 gas pressure. From these experiments, we found that the double-peak current waveform appeared at high pressure and high voltage conditions. We also analyzed the mutual correlation of waveforms between a single current and the light emission.Moreover, we obtained experimental evidence of filmentlike light image appearing at the PD tip under the same condition with double-peak current waveform. From the electric field analysis around the needle electrode tip, we believe that the filamentlike light image expands beyond the critical electric field of SF 6 gas. Thus, we concluded that these current waveforms with double peaks showed evidence of leader-type PD, leading to breakdown. Finally, we could point out that leader-type PD should be distinguished and measured for the diagnosis of GIS insulation performance. © 1999 Scripta Technica, Electr Eng Jpn, 129(4): 5865, 1999